[KevinFromTexas]

Riverside Drive through Butler Park and Auditorium Shores isn't particularly bad to cross as a pedestrian. Still, let's consider the benefits of sinking Riverside Drive. Basically they would cut and cap it. It wouldn't be a true tunnel, rather a trench with structural concrete placed on top to create a bridge over the trench. The benefit would be a larger uninterrupted park space. There would be more park space without the above ground street, plus all the road infrastructure and signage would go away. The traffic benefit for the street would be that even during huge festivals the street could remain open. So even during the 4th of July fireworks display and large concerts/festivals, the street wouldn't need to be closed.